The use of measurements of plasma cortisol to determine responses to stressful events has been investigated in adults, children and infants. Few studies have documented levels of plasma cortisol in preterm infants and none have documented levels of salivary cortisol. Preterm infants experience frequent procedures which are physiologically and behaviorally stressful. The acquisition of saliva to determine cortisol response could add to our understanding of preterm infants' responses to stressful procedures.